SCEC Award Number 15086 View PDF
Proposal Category Collaborative Proposal (Data Gathering and Products)
Proposal Title Advancing time series comparison and analysis for application to the Community Geodetic Model
Investigator(s)
Name Organization
Thomas Herring Massachusetts Institute of Technology Michael Floyd Massachusetts Institute of Technology
Other Participants
SCEC Priorities 1d, 1e, 5b SCEC Groups Geodesy, Transient Detection
Report Due Date 03/15/2016 Date Report Submitted 03/13/2016
Project Abstract
 The goals of our work are to develop time series analysis for the combined product that will form the basis of and be distributed as part of GPS component of the SCEC Community Geodetic Model (CGM). We investigate techniques for the accurate and consistent recovery of secular velocities using a combination of time series from different analysis centers that make their products available for this purpose in the presence of time-dependent deformation, such as post-seismic decays. In forming combined GPS time series we will focus on (1) weighting of individual contributions and assessing the correlations between series, (2) quantifying and accounting for mean differences between analyses even when they have realized in the same reference frame and (3) assessing how to best treat scale estimates when transforming coordinate systems.
Intellectual Merit This work is a core piece of the production of the GPS component of the SCEC Community Geodetic Model. This product will eventually act as a resource for both the scientific and wider public community. Consensus for creation of time series and crustal velocities is required due to the current variety of projects that generate relevant products through a variety of approaches, which may result in subtle but significant differences in interpretation.
Broader Impacts Geodetic data products are now incorporated into probabilistic seismic hazard analyses (PSHAs), and they accuracy of these relies on an accurate, widespread and dense fault displacement and crustal velocity estimates. Beyond the scientific use of these PSHAs, they form a part of community education and outreach products, where they are visualized for public consumption.
Exemplary Figure Figure 1. Comparison of the vertical component of time series for site P113 with and without the estimation of scale when realigning to a common reference frame. (a) Publicly-distributed PBO product (no scale estimated); (b) Publicly-distributed UNR NA12 [Blewitt et al., 2013] product (scale estimated); (c) Publicly-distributed UNR IGb08 product (no scale estimated); (d) Same as (a) except with scale estimated during alignment to the reference frame. The difference between (b) and (c) or (a) and (d) demonstrates directly the difference between time series where the scale is (b,d) and is not (a,c) estimated, given that these time series come from the same analysis center but are aligned to the reference frame in different ways. (c) compares well to (a), as expected for two time series created without estimating scale. (d) compares well to (b), as expected for two time series created with scale estimated.